I have been noticing similar issues last season with my dvn22 micron gauge . i actually use the 3/8 hose directly from vac pump to suction side of condenser valve with appion core tool hooked up, then the micron gauge hooked directly to another appion core tool on high side of condenser

So after reaching desired micron reading i close ball valve on suction side and wait.. all seems fine but after i then close ball valve on micron gauge core tool it immediately rises and fast,, makes me think theres a leak in the micron gauge..

I spoke in depth to aJB engineer at the expo about this and he says he doesnt think theres anything wrong with gauge long as it doesnt rise past 9000/1(whatever that means in English :) ) and says its normal for some rise due to moisture etc just like a system/.

im not sure i believe him but this thread along with my issues is making me not trust this micron gauge and others ive owned in the past.

feedback?? letys continue this conversation as it can help a lot in the field..the good thing is he told me to test with a tank like this thread suggests and see what the actual rise stops at, if i still feel its faulty he promised to pay for me to send it back and they will re calibrate and test for free even if its out of warranty..

My JB does the same thing when valved off by itself. Works great. Had it for years still kept in its original plastic case inside a meter bag. I think it goes back to once you valve it off by itself there is too little volume in the core tool and gauge to hold a vacuum.

02-04-2013, 07:57 PM

Pascone10

Also when you close a ball valve there is believe it or not an area where a higher pressure is stuck until you close the valve. IF you close the ball valve or you CRT you usually can hear the air if it was sitting in the truck awhile..

02-04-2013, 09:15 PM

Chuck

Yes, especially if you just got done doing a 600 psi nitro test!

Quote:

Originally Posted by Pascone10

Also when you close a ball valve there is believe it or not an area where a higher pressure is stuck until you close the valve. IF you close the ball valve or you CRT you usually can hear the air if it was sitting in the truck awhile..

02-04-2013, 09:29 PM

jim bergmann

Dave,
I noticed several things.

You need to be able to isolate all of the hoses completely from the system when pulling a vacuum. You need core tools and a brass connector to isolate your vacuum gauge. All hoses, even Appion hoses leak. They just leak at a lower leak rate then standard hoses.

All connections leak, again it is the leak rate that matters.

The recovery tank valves my not be rated for vacuum. Make sure that the valve is completely back seated. The packing might be leaking. I see that a lot. Try an empty refrigerant cylinder, they are a lot less likely to leak.

There is nothing wrong with using the vacuum rated manifold, it allows for several more connections if you are working on a commercial system. It is a must have for very large systems to get the required flow from a larger pump. For residential systems, a simple brass tee will do.

Read through this vacuum primer before you throw in the towel, you are making a few simple mistakes, I know the information here will help. If you have questions, PM me with a phone number to help.

When the core tools are isolated you are looking at leak rate, when open it is really pull down rate. Pull down is negative, rise is positive.

Cycle your core tools during pull down. A small amount of gas/air gets trapped in the valve packing. This will minimize the initial rise when you isolate the hoses.

Leak rate is in microns/second. If you multiply the leak rate x 60 seconds/min x 10 minutes you can get the approximate rise after 10 minutes. Under 500 is acceptable. at a leak rate of .2 microns/second that would rise 120 microns over 10 minutes.

The calibration of the FP and theBluvac were very close at low vacuum. It is typical for the Bluvac to be faster simply due to the technology used. They also may have different calibration points. Maybe one at 500 microns and one at 250. I am not sure. But I have seen a lot of different vacuum gauges do not agree until they are in a deeper vacuum.